1. Technical Field
The present invention relates to an apparatus and a method for controlling transmit power operated in a unidirectional communication system.
2. Description of the Related Art
Generally, in a bidirectional communication system in which a mobile terminal and a base station are present, the mobile terminal may measure a strength of a signal transmitted from the base station and input thereto, and the base station may measure a strength of a signal transmitted from the mobile terminal and input thereto.
However, in a system using only unidirectional communication from the mobile terminal to the base station, the base station may measure a strength of a signal transmitted from the mobile terminal and input thereto. However, since the base station does not transmit a signal, the mobile terminal may not measure a strength of a signal output from the base station. Since the mobile terminal may not know path loss of a transmitter and a receiver, in the case in which the mobile terminal recognizes its position and a position of the base station, a transmit output of the mobile terminal is generally controlled depending on a distance on the basis of information on the position of the mobile terminal and the position of the base station.
However, in the case of using only the information on the positions, path loss between the mobile terminal and the base station is estimated using only the information on the positions. In this case, a problem that the path loss may be changed when a specific object, for example, a mountain, a building, air, a fog, a cloud, rain, snow, or the like, is present between the mobile terminal and the base station may be overlooked.